1. Field of the Invention
This invention relates to a three-phase slotted armature winding wherein coils are laid in stator core slots such that a winding in each pole in each phase has a multilayer lap winding arrangement.
2. Description of the Prior Art
In the following description, a winding comprises a coil or a plurality of series coils laid in slots for forming each pole and each coil comprises a plurality of turns of an electrical wire. A winding forming a pole is referred to as a pole winding.
A lap winding and a concentric winding are known as coil arrangements in a three-phase armature winding. In the lap winding, coils having the same configuration and coil pitch are placed one upon the other in sequence and laid in the slots. Electric characteristics of each phase are advantageously balanced since the coils have the same configuration and the winding resistance and leakage reactance of each phase are equal. However, the coil inserting work cannot be automatized since the coils of different phases are placed one upon the other into double-layers and laid in one and the same slot, resulting in a disadvantage that the work needs to be manually performed by worker.
On the other hand, in the concentric winding, a plurality of coils different in the coil pitch in a winding of each pole of each phase are laid in the slots so that the coils are distributed so as to be concentric about the pole center. The coils can be laid in the slots by a coil inserting machine generally called automatic coil inserter and the inserter has been widely used for its superior productivity.
Japanese Published Patent Application (Kokoku) No. 47-42881 discloses a double-layer lap type armature winding which has a coil arrangement wherein the automatic coil insertion can be performed at every one pole winding by the automatic coil inserter. In this case, a coil transposing work is eliminated wherein a coil side of the initially laid winding is taken out of the slot when a final winding is laid in the slot, and coil sides of the final and initial windings are laid in the empty slot with the coil side of the initial winding placed on that of the final winding. However, in the case of the three-phase four pole arrangement, for example, the coil inserting operation needs to be performed at twelve times, which number corresponds to the number of poles.